1. Field of the Invention
The present invention relates to techniques for switching between graphics sources in computer systems. More specifically, the present invention relates to a method and an apparatus for reducing power by switching between graphics sources in a computer system.
2. Related Art
Rapid advances in computing technology have made it possible to perform trillions of computational operations each second on data sets that are sometimes as large as a trillion bytes. These advances can be largely attributed to the exponential increase in the size and complexity of integrated circuits. Unfortunately, the increase in size and complexity of integrated circuits has been accompanied by a similar increase in their power consumption.
In a parallel development, the rapid proliferation of broadband wireless networks has created an insatiable demand for portable computer systems. Unfortunately, portable computer systems usually have stringent power constraints due to the limited battery power that is available to them. These developments have created a strong need for techniques and systems to save power.
Advances in 3D graphics technology has led most of the modern computer systems to use dedicated graphics processors (sometimes referred to as graphics processing units (GPU)) to drive graphics display devices. Unfortunately, today's GPUs consume a large amount of power, which severely shortens the battery life of portable computer systems, and also causes heat dissipation problems.
During a graphics display operation, there are often times when very little graphics processing is needed, for example, when the user is reading a document on the display. Unfortunately, prior art graphics processors cannot switch to a sufficiently low-power mode in order to conserve enough power during these “low activity” periods.
One solution to save power during such “low activity” periods is to switch the display from a high-power graphics source (e.g., a high-performance GPU) to a low-power graphics source (e.g., a low-performance GPU). Ideally, this switching operation should be invisible to the user, so that the system can seamlessly switch back and forth between the different graphics sources as the graphics processing demands change, or as the system's need to limit power consumption changes.
A prior art technique provides a mechanical switch which allows a user to switch between a lower-performance graphics source and a higher-performance graphics source. However, this brute-force technique requires the user to fully re-initialize the computer system each time the user switches from one graphics source to another. Requiring a user to re-initialize the computer system to switch from one graphics source to another is simply not acceptable in many situations. An initialization process is one of the most disruptive operations that can be performed on the computer. Typically the user has to save all his or her work before re-initializing the computer, which can take a considerable time to complete. Furthermore, the user must first decide whether their graphics processing requirements will be high or low in the near future, and then wait for the system to re-initialize, and then be willing to wait for another re-initialization if the requirements change.
Hence, what is needed is a method and an apparatus that facilitates rapid and/or seamless switching between different graphics sources.